FI111965B - Aminoalkandiphosphonic acids in the bleaching of pulp - Google Patents

Abstract

PCT No. PCT/EP94/03546 Sec. 371 Date Feb. 8, 1995 Sec. 102(e) Date Feb. 8, 1995 PCT Filed Oct. 26, 1994 PCT Pub. No. WO95/12029 PCT Pub. Date May 4, 1995A process for the bleaching of pulp comprising the step of bleaching the pulp with hydrogen peroxide and an effective amount of at least one biodegradable 1-aminoalkane-1,1-diphosphonate chelating agent to enhance the bleaching of the pulp, is disclosed. Also disclosed is the use of a 1-aminoalkane-1,1-diphosphonate to enhance the bleaching of pulp with hydrogen peroxide, as well as the pretreatment of pulp with a 1-aminoalkane-1,1-diphosphonate prior to the step of bleaching with hydrogen peroxide. Finally, the deinking of pulp in the presence of 1-aminoalkane-1,1-diphosphonate is also disclosed.

Description

111965

Aminoalkane diphosphonic acids in pulp bleaching

FIELD OF THE INVENTION This invention relates to a process for bleaching pulp with hydrogen peroxide in the presence of aminoalkane diphosphonic acid and pretreating the pulp with aminoalkane diphosphonic acid prior to bleaching with hydrogen peroxide. The present invention also relates to the use of aminoalkane diphosphonic acid in pulp pre-treatment, pulp bleaching with hydrogen peroxide, and pulping.

Background of the Invention

After manufacture, the pulps may vary in color depending on the type of wood, the method of manufacture and other factors. Many types of pulp require casting to produce pulp with the desired level of brightness. Brightness is determined by measuring the reflectance (reflectance) in the blue region (457 nm) using magnesium oxide (100% brightness) as a standard.

The most commonly used substance for pulp bleaching is hydrogen type 20 oxide because it is cheap and effective in bleaching. Many different pulp bleaching methods are known which use hydrogen peroxide as a bleaching agent. Some examples of such methods are disclosed in U.S. Patent Nos. 4,798,652 and 4,732,650. From these patents it can be seen that the process for bleaching wood pulp often includes a pretreatment step and a bleaching step.

US 4,798,652 discloses the use of diethylene triamine pentaacetic acid (DTPA) in the pretreatment of pulps prior to bleaching with hydrogen peroxide. The pretreatment is generally carried out at a pulp consistency of less than 5%, and the chelating agent is preferably t ♦ · 1 '_ί a relatively strong complexing agent.

US Patent 4,732,650 discloses the use of chelating agents in a pretreatment step prior to bleaching pulp with hydrogen peroxide. Typical ketal formers used in the pretreatment step include ethylenediaminetetraacetic acid (EDTA), DTPA, triethylenetetraamine hexacetic acid (TTHA), and N- (hydroxyethylene) diaminitric acid (EDTA).

EP-A-0 141 355 relates to a process for bleaching pulp using a combination of phosphonic acids, polyhydroxycarboxylic acids and phosphates. It is stated therein that the individual constituents have insufficient bleaching power and / or do not sufficiently (or even negatively affect) the stability of the peroxide solution. The following aminoalkanediphosphonic acids are specifically mentioned: N, N-bis (carboxymethyl) -1-aminoethane-1,1-diphosphonic acid, N- (2-carboxyethyl) -1-aminoethane-1,1-diphosphonic acid, 15 N , N-bis (hydroxymethyl) -1-aminoethane-1,1-diphosphonic acid.

In addition, Comparative Example 2 of EP-A-0 141 355 employs a bleaching composition containing 1.9% hydrogen peroxide, 1.7% NaOH and 1% N, N-bis (carboxymethyl) -1-aminoethane-1,1- diphosphonic acid.

20 Article "Chelating Agents in the Pulp and Paper

Industry, "Hart, J. Roger, Tappi Journal 64 (March 1981), No. 3, 43-44, discusses the role of chelating agents in bleaching pulps. This article notes that chelating agents can be used both in pulp pre-bleaching and bleaching processes. Preferred chelating agents are EDTA and DTPA as the preferred chelating agent in the bleaching solution during the bleaching step '*' '.

i * I

'·: · * Another related article is' 30' The Effect of DTPA on Reducing Peroxide Decomposition,

Bambrick, D. R., Tappi Journal 66 (June 1985), No. 6,; 96-100, in which the article discusses in detail the role of DTPA in hydrogen peroxide bleaching of wood pulp when used in combination with silicates and magnesium compounds (»35. In the article" Hydrogen Peroxide: Stable I »» 111965 3 Bilization of Bleachin Liquors " , Kutney, GW, Pulp & Paper Canada 86 (1985), No. 12, 182-189, provides a detailed summary of a wide variety of compounds used to stabilize hydrogen peroxide bleaching solutions and thereby provide a pulp of higher brightness. Various chelating agents have been mentioned, including EDTA, DTPA and nitrile acetic acid (NTA).

In addition, the article "Improving Hydrogen Peroxide 10 Bleaching of Mechanical Pulp: The Effect of Silicate Dose and Other Additives" by Burton, J.T., et al., Pulp & Paper Canada 86 (1987), No. 6, 144-147, provides various on the effects of additives on pulp bleaching with hydrogen peroxide. The chelating agents used included DTPA and diethylenetriamine pentamethylene phosphonic acid (DTMPA, also abbreviated as DTPMPA). The use of these additives in the bleaching solution is ultimately intended to replace the silicate additives.

It is apparent from the latter two articles 20 that it is desirable to reduce the concentration of silicates in current pulp bleaching systems. In addition, the chelating agents used in pulp bleaching have the disadvantage that they are somewhat completely non-biodegradable. One of the ongoing research efforts in the pulp bleaching industry is to develop more environmentally friendly bleaching systems, for example by reducing silicate content; · By providing more biodegradable additives for bleaching and / or improving the activity of the bleaching solution so that it can result in the use of »30» more bleaching solution and achieve the same level of brightness.

,,. One article that attempts to demonstrate mass · ·; the desirability of reducing the amount of silicates used in the formulation is still "Chelant Optimization in De-Inking Formulation", Mathur, I., Pulp & Paper Canada 94 35 (1993), No. 10, 55-60.

I I I

111965 4 that EDTA, HEDTA, DTPA and DTPMPA are used for pulping. DTPA is named as the best chelating agent in the de-inking process.

Thus, the primary object of the present invention is to provide an efficient pulp bleaching system which is more environmentally friendly than current commercial bleaching systems using EDTA and / or DTPA chelating agent with or without silicates.

This and other objects and advantages of the invention will become apparent from the following summary and detailed description.

SUMMARY OF THE INVENTION This invention relates to a process for bleaching wood pulp, which process comprises bleaching wood pulp using hydrogen peroxide as the primary bleaching process, characterized in that said bleaching step is carried out in an effective amount of at least one biodegradable 1-aminoalkane in the presence of formula I, 20

OX Ri OX

III

0 = P-C-P = 0 (I)

I I I

OX N OX

/ \ Γ \. R2 R2 wherein R3 is hydrogen; R 2 and R 3 are hydrogen, C 1 -C 22 alkyl groups, C 5 -C 6 cycloalkyl groups, C 1 -C 4 alkanol, groups such as -CH 2 CH 2 OH, and carboxyalkyl groups containing up to 10 carbon atoms, such as -C 0 CH 3, or R 2 and R3 30 together with the nitrogen atom may form a piperidino,,,, pyrrolidino or morpholino group; and X is hydrogen, alkali metal or ammonium; to promote the bleaching of wood pulp.

In another embodiment, the present invention relates to Formula I

use of a chelating agent according to claim 1 to promote bleaching of pulp 35 with hydrogen peroxide.

The present invention also encompasses the pretreatment of pulp in the presence of a chelating agent of formula I, as well as the use of a chelating agent of formula I in deinking processes.

5 Brief Description of the Drawings

Figure 1 is a graph illustrating the calculated conditional stability coefficients of (4-morpholinylmethylene) bisphosphonic acid for complexation of various metal ions.

Fig. 2 is a graph depicting calculated EDTA coefficients of stability for complexation of various metal ions.

Figure 3 is a graph depicting the calculated DTPA conditional stability coefficients for the complexation of various metal ions.

Figures 4-17 are exemplary curves 5-9. They are explained in the corresponding examples. DETAILED DESCRIPTION OF THE INVENTION Chelating agents corresponding to Formula I above and methods for their preparation are known from a number of publications, including e.g. "Synthesis of 1-Dialkylaminoalkylidene Diphosphonic Acids and Their Properties for Complex Formation", Fukuda, M., et al., Yakagaku 25 (1976), No. 6, 362-364; U.S. Pat. Nos. 3,899,496 and 3,979,385; and the article "Acidity and: Complex Formation Properties of Some (Aminomethylene) Bis ·; Phosphonic Acids", by Gross, H., et al., Zhurnal Obshchei: Khimii 48 (September 1978), No. 9, 1914-16 ( hereinafter referred to as Gross).

Several publications of formula I have been mentioned in this publication. uses of chelating agents, which include water softening, use in cleaning products to remove coarse-grained · · · · · · · in fabric washing, use in dyeing: · baths and use as builders in laundry compositions. However, none of these publications have suggested the use of t 1119656 in formula I in pulp bleaching processes or pulp bleaching solutions, nor does it suggest that these substances are potentially biodegradable.

Further, the stability coefficients of the complexes formed by some compounds of formula I are known from Gross's publication. Using these stability coefficients, the ability of chelating agents to form complexes can be predicted. However, the stability coefficients are not the best indicator in this regard since the formation of the 10 complex is highly dependent on the pH of the system. Thus, the best benchmark is a conditional stability coefficient that takes into account pH variations and is explained in Akzo Technical Leaflet 217.

With reference to Figures 1-3, it can be seen that the conditional stability coefficients calculated for 4-morpholinylmethylene-1,1-diphosphonic acid, a compound of formula I above, are much lower than the corresponding ones calculated for EDTA and DTPA. Based on this, it could be expected that said compound of this invention will have a much lower chelating activity than EDTA or DTPA. Thus, based on these data, 4-morpholinylmethylene-1,1-diphosphonic acid was expected to perform much worse in pulp bleaching processes than DTPA.

Surprisingly, however, the present inventors have: found that the compounds of this invention act; at least as well as in pulp bleaching processes; EDTA or DTPA and thus provide a significant improvement to the pulp bleaching process by providing known chelator-30 biodegradable substitutes that are more environmentally friendly. EDTA and DTPA are known to be practical It is not biodegradable.

'*' The term "biodegradable", as used in this patent application, means that a significant percentage of the 35 substances are degraded in the semi-continuous activated sludge test «* ·» · 111965 7 (in the SCAS test) and in the closed bottle test within 28 days. Further details on the test methods used to determine biodegradability are given in the examples below.

A typical pulp bleaching process includes at least two steps, a pretreatment step and a bleaching step. The pretreatment step reduces the amount of impurities in the pulp and, in particular, lowers the metal ions in the pulp before the bleaching step. In accordance with the objects of this invention, the compounds of formula I may be used in pulp pre-treatment.

Based on their conditional stability coefficients, the compounds of Formula I could be expected to perform poorly in bulk pre-treatment. However, the present inventors 15 have found that the compounds of formula I provide a useful alternative to the EDTA and DTPA chelating agents commonly used in pulp pre-treatment, while providing the additional advantage of biodegradability. This is a major advantage, as the mass manufacturing industry is 20 notorious for producing large amounts of waste, which requires investing huge sums of money in waste management.

In a typical pretreatment step, a large amount of pulp is flushed with water containing the compound of formula I, optionally at elevated temperature. In this way, many water-soluble impurities are obtained by rinsing - *: · * the pulp and the compound of formula I; the metal ion content of the pulp can be significantly reduced. This pre-treatment of the invention can be charged to both chemical (kraft and sulfite) and honey. cyanic pulps such as SGW, PGW, TMP and CTMP.

More particularly, the pretreatment may be carried out using 0.1 to 2.0% by weight of the chelating agent 35 of Formula I with a treatment duration of only 5 minutes or, if desired, even overnight. More preferred processes use a 5 minute to 4 hour pretreatment at a temperature of 40 to 90 ° C and a pH of 5 to 9. The pulp consistency in the pretreatment is typically 1 to 5%, preferably 1 to 3%. In addition, if desired, the same additives mentioned below as suitable for the bleaching step may be used in the pretreatment step.

This invention also relates to a pulp bleaching step. The process is suitable for bleaching both chemical and mechanical pulps and recycled pulps. Suitable pulps include in particular mechanical pulps SGW, PGW, TMP and CTMP as well as chemical pulps for kraft and sulphite pulps. In a preferred embodiment, the process is used for bleaching mechanical pulp.

In the process of the present invention, a bleaching temperature of 40 to 95 ° C, preferably 50 to 75 ° C, is used. The dry weight of the pulp is typically 5 to 40% of the total weight of the pulp and the pulp is pre-treated before bleaching. The bleaching time is generally 10 to 120 minutes, and more preferably 20 to 40 to 90 minutes. Bleaching is generally carried out in a pH range of 9 to 12 and even more preferred is a pH range of 10 to 12.

Typically, 0.1 to 3.0% by weight of hydrogen peroxide, based on the total weight of the pulp, is used as the bleaching agent in the process. In addition, 0.01% to 2.0% by weight, based on a total weight of 25%, of one or more bioha-. a compound of formula I. The preferred amount of the compound of formula I depends to some extent on the heavy metal content of the pulp to be bleached. Larger metal. concentrations require more of the chelating agent of formula I.

In addition to the bleaching agent and the chelating agent, other conventional additives may be used in the bleaching process. In addition to the chelating agent, for example, 0-3% by weight, based on the total weight of the pulp, of a conventional silicate additive may be used. In addition, magnesium sulfate may be used in the process of this I · 111965 9 from 0 to 0.2% by weight, based on the total weight of the pulp. The silicate and magnesium sulfate component are typically added to buffer the solutions to maintain a relatively constant pH throughout the bleaching step.

Other additives that may be used in the process of this invention in addition to the chelating agent of formula I include products such as citric acid, DTPA, DTPMPA, EDTA, gluconates and lignosulfonates, which may also have some chelating activity. In this embodiment, where other additives are used, the chelating agents of formula I are used to replace some of the known chelating agents in order to make the pulping process more environmentally friendly. The latter are optional additives which may or may not be used in the process of this invention. If used, these ingredients are employed in conventional amounts of from about 0.01% to about 2.0% by weight based on the total weight of the pulp.

From the Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Edition, 1982, Vol. 19, p. 413, it is known that mechanical pulps have initial brightness values of ·25 ranging from 50 to 65% (GE brightness). There is also a feeling: · ,. It is understood that every 1% increase in brightness is meaningful and commercially attractive, as long as the cost of such an increase in brightness is not disproportionate.

Despite the fact that the conditional stability coefficients of the chelating agents of this invention predict them to be inferior to the commercially used bleaching agent DTPA, tests have shown that the chelating agents of this invention produce an increase in lightness of the order: * DTPA. This result is completely unexpected. In addition, the chelators of the present invention have the significant and unexpected additional advantage of having a significant degree of biodegradability.

Preferred chelating agents of formula I for use in the process of this invention include 5-morpholinylmethylene-1,1-diphosphonic acid (MMBA), [(dimethylamino) methylene] bisphosphonic acid (DMAMBP), (1-aminomethylidene) bisphosphonic acid (1-aminoethylidene) bisphosphonic acid (AEBP). Most preferred chelating agents are those compounds of formula I which have a high degree of biodegradability. These include compounds of formula I wherein R 3 is hydrogen.

In another embodiment, the invention relates to the use of compounds of formula I for promoting bleaching of hydrogen peroxides. This use is essentially as described above for the pulp bleaching process.

In another embodiment, the invention relates to the use of chelating agents of formula I in deinking collected pulp products. The deinking is generally carried out using hydrogen peroxide, and therefore the chelating agents of this invention can also be used for deinking paper. The recycled paper raw material typically includes newspapers, magazines, etc.

• The de-inking is done using hydrogen peroxide in a basic environment in a conventional manner except that the de-inking process uses the formula I; those chelators. The chelating agent is generally used in an amount of 0.1 to 2.0% by weight. Of course, mixtures of two or more chelating agents can also be used within the scope of this invention. Additionally, optional deodorizing additives such as silicates may be used if desired or desired.

: The invention will be further illustrated by the following examples: ”: 35 which are not limiting.

Ί11965 11

Example 1

Closed Bottle Test for Biodegradation of 4-Morpholinylmethylene-1,1-Diphosphonic Acid (MMBA) 5 Secondary activated sludge and primary sedimented waste were collected from the WWTP Niewgraaf waste treatment plant until required and stored weekly until and after storage. These samples were used in a sealed bottle test of 250-300 ml with glass stoppers for biological oxygen demand (BHK) determination and in a SCAS test in 150 ml SCAS units.

The aqueous stock solution was prepared from MMBA 15 (1.0 g / L) and buffer containing K 2 HPO 4 (155 g / L) and NaH 2 PO 4 * H 2 O (85 g / L). An aqueous nutrient medium for a closed bottle test was prepared from water, KH2PO4 (8.5 mg / L), K2HPO4 (21.75 mg / L), Na2HPO4 ♦2H2O (33.3 mg / L), MgSO 4 * 7H 2 O (22.5 mg / L), 20 CaCl 2 (27.5 mg / L) and FeCl 3 · 6H 2 O (0.25 mg / L). Ammonium chloride was omitted from the culture medium to prevent nitrification.

The sealed bottle test was conducted according to the following sources: OECD Guilines for Testing Chemicals, Section; 25 3: Degradation and Accumulation no. 302 A, Inherent Βίοι degradability, Modified SCAS Test (1981), Paris Cedex, ·: ··: France; EEC, 1988: Official Journal of the European Communi- ties, L133, 30.05.1988, Part C: Methods for the Determination of Ecotoxicity. Biodegradability Modified SCAS Test; 30 and ISO / TS / SC 5 Water Quality - Evaluation of Aerobic ..Biodegradability of Organic Compounds in Aqueous Medium-Semi-Continuous Activated Sludge Method (SCAS 1991). Test ·; was performed under diffused light at 20-25 ° C.

: Three flasks containing only 35 inoculum and three flasks containing test substance and inoculum were used. The concentration of test compound in the flask was 2.0 mg / L and sodium acetate 6.7 mg / L. The inoculum was diluted in closed flasks to 2 mg (DW) / L. Each of the prepared solutions was divided into its own group of BHK flasks so that the flasks were completely filled and did not contain air bubbles. At zero time, flasks were immediately analyzed for oxygen using an oxygen electrode. The remaining bottles were sealed and incubated in the dark at 21 ° C. Oxygen concentration 10 was determined on days 7, 14, 21 and 28.

The standard closed flask test was departed from one ratio, namely by using a special funnel to measure the oxygen concentration from the same flask three times. The sealed flask test was extended by measuring the course of oxygen depletion in the flasks using the same special funnel that was accurately fitted to the BHK flasks. An oxygen electrode was then placed inside the BHK flasks to measure the oxygen content and the medium removed by the electrode was collected in a funnel. After removal of the electrode, the collected media flowed from the funnel back to the flask, after which the funnel was removed and the flask was resealed.

Theoretical oxygen demand (THK) was calculated using MMBA molecular weight. Biological Oxygen Demand (BHK) was calculated by dividing actual oxygen demand by the concentration of test substance in a sealed bottle. Biodegradation: "% is the ratio of BHK to THK. The results are shown in Table 1.

\% 4 111965 13

Table 1 Oxygen consumption and percentage biodegradation of MMBA. The sealed flask was inoculated with slurry from day 0 and 28 of the SCAS test.

5 - Day 0 Day 28

Time Oxygen Demand Biodegradation Oxygen Demand Biodegradation (%) mg / l% (%) 10 0 0.0 0 0.0 o 7 0.2 12 1.4 88 14 0.3 19 1.5 94 21 0.7 44 1.6 100 28 0.8 50 1.7 100 15 42 1.0 63 - -

Example 2 SCAS Test To determine the biodegradability of 4-morpholinylmethylene-1,1-diphosphonic acid 20 MM (MMBA), the same substances as in Example 1 were used in the SCAS test. Stock solution was prepared from MMBA (1.0 g / l) and buffer containing K 2 HPO 4. (155 g / L) and NaH 2 PO 4 · H 2 O (85 g / L). The SCAS test was performed according to the instructions in Example 1 25. The test was performed under diffused light at 20-25 ° C.

Each SCAS unit was filled with activated sludge: (150 mL), and aeration was started. After 23 hours, the aeration was stopped and the slurry was allowed to settle for 45 to 30 minutes. The units' walls should be cleaned before landing. to prevent solids accumulation above the liquid level, using a different brush for cleaning each unit to prevent cross-contamination. The tap was opened and 100 mL of excess was drained. Subsequently, primary sediment (99 ml) and concentrated phosphate buffer (1 ml) were added to each of the remaining slurries in each SCAS unit, and the aeration was resumed. The units were fed daily with primary debris.

On day 0, the different sedimented slurries were mixed with each other and the resulting composite slurry (50ml) was added to each SCAS unit. Primary sediment (94 ml), deionized water (5 ml) and concentrated phosphate buffer (1 ml) were added to the control unit, and to each test unit was added primary sediment (94 ml), MMBA stock solution (5 ml) and concentrated phosphate (5 ml). 1 ml). Aeration was continued for 23 hours. The filling and removal procedure described above was repeated six times a week throughout the test.

The test differed slightly from the conventional SCAS procedure in that the filling and removal procedure was repeated six times per week and not daily, six times a week concentrated phosphate buffer (1 ml) was added to maintain the pH constant in the SCAS unit and the removal samples were calculated using Schleicher & Schull membranes (cellulose nitrate membranes) with a pore size of 8 µm.

, 'Unleached organic carbon (NPOC) was determined

acidifying the filtered samples and injecting them into the Dohrmann DC-190 NPOC. PH of the supernatant solution

; · Determined with a pH meter connected to a microcomputer

la Consort P207, and dissolved oxygen concentrations were determined electrochemically using an oxygen electrode (WTW

• t *

Trioxmatic E0 200) and Meter (WTW 0X1 530). Temperature,> 30, was measured on a Control One (manufactured by IBT, Rotter-; Dam). The dry weight (DW) of the inoculum was determined by filtering a · · * * active slurry (100 ml) using a pre-weighed Schleicher & Schull filter with a pore size of 8 µm, drying the filter for 1.5 hours at room temperature. 104 ° C and weighing the filter after cooling.

The percent discharge in the SCAS test was calculated using the following equation: 5

Displacement (%) = 100 x [CT - (Ct - Cc)] / Cx CT concentration of test compound in sedimented waste at the beginning of the aeration period, expressed as non-leached organic carbon.

Ct = is the concentration of unclean organic carbon at the beginning of the aeration period, determined from the supernatant of the test unit.

Cc = is the concentration of unclean organic carbon at the beginning of the aeration period, determined from the blank solution of the reference unit. The results are shown in Table 2.

t «» 1 »111965 16

Table 2 NPOC Concentrations in Reference and Test Unit Removal and Calculated MMBA Percent Removal 5 Time NPOC, Comparison NPOC, Test Removal (d) (mg / 1) (mg / 1) (%) -4 14.7 14.0 -1 15.1 15.1 10 0 13.1 13.7 1 13.0 14.3 91 2 14.9 16.4 89 3 13.7 17.0 76 4 2.4 15.1 80 15 6 13.9 16.5 81 7 14.0 16.9 79 8 13.1 14.9 87 9 14.5 16.1 88 10 13.7 16.9 77 20 11 13.8 16.5 80 14 14 , 7 16.3 88 16 15.1 17.1 85 18 18.5 18.6 99 21 15.8 17.2 90 j '· 25 23 14.7 17.4 80 ·: ·: 25 14.5 18.6 70: 28 15.1 17.8 80 30 9.3 17.7 39 32 9.1 15.2 55 ..... 30 35 10.4 13.4 78

Example 3 • Thermomechanical pulp (TMP) having a consistency of 20%, an initial brightness of 57.7% and a metal content of 1.9 mmol / kg]. 35 (Fe, Cu, Mn, Zn), bleached at 120 ° C for 120 minutes using 10 kg and 30 kg hydrogen peroxide (reference) / t100 combined with equivalent molar amounts of DTPA-H5 (commercially available bleach additive) , 0.97 kg / t100) or MMBA (additive according to the invention, 0.72 kg / t100) in the presence of 30 kg / t100 of silicon 5 and magnesium sulfate (1 kg / t100). The bleaching solution had an initial pH of 11.5 as measured at 25 ° C. The results are shown in Table 3. The pretreatment step did not contain chelating agents and thus consisted only of a water wash at 25 ° C and pH 6.2.

Table 3

Brightness (%), Brightness (%), Brightness (%),

H 2 O 2 Comparison DTPA MMBA

15 -

Unbleached 57.7 10 kg / t100 64.5 66.9 65.5 30 kg / t100 70.0 72.4 73.0 20 t100 refers to metric tonnes of dry solid mass. Example 4 ···: [(Dimethylamino) methylene] bisphospho: ··ic acid and (1-aminoethylidene) bisphosphonic acid (AEBP) were synthesized by known methods and tested for their hydrogen peroxide stabilizing effect.

A. Measurement of hydrogen peroxide 0-1% Using a diluent set up to dilute 96 μΐ to 15 ml, a sample of hydrogen peroxide solution (96 μΐ) was taken. The solution was placed in a stirred beaker containing a color reagent prepared by diluting sulfuric acid (173 g) and a 15% (m / v) solution of Ti (SO 4) 2 (45 mL) in 500 mL: demineralized water to give a stock solution, and then dilution. 35 stock solution (58.5 ml) further to 1 liter demineralisol%. with water. 15 ml of a yellow colored mixture were obtained.

111965 18 This solution was used in a cuvette and the absorbance was measured to determine the hydrogen peroxide content.

B. Testing for the stabilizing effect of hydrogen peroxide

Fourteen flasks of polyethylene were filled with a solution of metal 5 (5.0 mL) containing 20 ppm Cu (II), 40 ppm Fe (III) and 50 ppm (Mn (II). One control flask was filled with water. to these flasks, except for one, a solution of a complexing agent (5.0 ml) containing 0.5% by weight of DMAMBP or AEBP in demineralized water and a solution of sodium p-phenolsulfonate (0, 1 mol / l, 10.0 mL) The total mass of each solution was adjusted to 30 g using demineralized water, then adjusted to pH 9.5 with either sodium hydroxide or hydrochloric acid as needed, and then the total mass of each solution was then adjusted to 45 g To the resulting solutions, a 10% solution of hydrogen peroxide was added.

Thus, solutions containing 20 2 ppm Cu (II), 4 ppm Fe (III), 5 ppm (Mn (II), 0.05% metal ion complexing agent, 0.02 mol were obtained. sodium p-phenolsulfonate / l and 1% by weight hydrogen peroxide.

The flasks were placed in a heat bath and shaken at 50 ° C (120 min -1). Every half hour • · 25 after the sample was taken quickly and placed in the · ·: reserved numbered flask. The samples were assayed for hydrogen peroxide using the procedure described above. I. The results are shown in Table 4.

Table 4 .... 30 - i ·

Complexing Remaining peroxide droplets in solution. (%) substance 30 min 60 min 90 min 120 min DMAMBP 92 90 87 86 35 AEBP 99 98 98 97 »· * *» 111965 19 This example demonstrates that DMAMBP and AEBP are effective in stabilizing hydrogen peroxide. Hydrogen peroxide stabilization is a good indication of the chelating ability of the compounds of this invention.

The above examples are provided for purposes of illustration and explanation only and are not to be construed as limiting the invention in any way. It is intended that the scope of the invention be defined by the appended claims.

10 Example 5 Ά. Experimental part

The pulp used in the following tests was TMP from the Scandinavian factory (unless otherwise stated). The pulp was removed from the storage tank before bleaching 15 and dewatered before the test started. Test conditions were as follows: Properties of untreated pulp:

Brightness: 60.2% (ISO)

Metal content 20 Ca: 590 ppm

Cu: 3 ppm

Fe: 2 ppm. Mg: 75 ppm: Mn: 34 ppm: 25 The mass was pretreated (Q phase) with various coils *: ·; formers under the following conditions:

; DTPA

Mass consistency: 5% Temperature: 50 ° C; ν <30 Time: 30 min

Added amount of DTPA: 2 kg / t pulp MMBA

: ': Mass consistency: 5% Temperature: 50 ° C and 90 ° C'. 35 Time: 30 min and 60 min

Added amount of MMBA: 2-6 kg / t pulp 20 111965

DMAMDPA

Mass consistency: 5% Temperature: 90 ° C Time: 30 min 5 DTPA added: 6 kg / h mass

The bleaching step (P step) was carried out as described below.

Mass consistency: 15%

Temperature: 60 ° C

10 Time: 2h and 4h with MMBA serving as a replacement for water glass Peroxide amount added: 10 - 40 kg / t pulp

The total alkali addition was optimized for each amount of peroxide added.

B. MMBA as complexing agent (Q-phase) 15 MMBA was tested as a complexing agent in the pretreatment step using TMP. After treatment, the pulp was dewatered and washed with deionized water, and then a fresh dewatering was performed before determining the metal content of the pulp. In the comparative experiment, pretreatment was performed with DTPA.

Figures 4 and 5 show the manganese and magnesium content of the pulp at the different pretreatment stages at different pH values. MMBA was effective at pH 8.5. The results show that MMBA is effective in reducing the manganese content in the pulp. However, it also lowers magnesium pi-; ness. Magnesium has a beneficial effect in the bleaching step, especially in the bleaching of kraft pulp. This example shows that 4 kg of MMBA lowered the manganese content of the pulp below 10 mg / kg. This is enough ... 30 to achieve a positive result in the bleaching phase.

The low metal content between pH 2 and pH 3 was; as a result of acid. Pretreatment experiments of 30 and 60 minutes show that 30 minutes is sufficient time: to achieve a low manganese content in the pulp.

! > 1 111965 21 C. Bleaching step (P-lie) After treatment with MMBA, the pulp was bleached with peroxide (40 kg / t pulp). Figure 6 shows the brightness after the P-stage using different amounts of MMBA and 5 2 kg DTPA in the Q-stage. In step P, peroxide, water glass and alkali (Eka standard) were used. 2 kg DTPA and 6 kg MMBA gave similar results in terms of brightness. MMBA is more sensitive to alkali changes and is not able to regulate manganese levels as well as DTPA.

10 D. Addition of manganese in bleaching step

When bleaching TCF for kraft pulps, it is often necessary to add extra magnesium in the bleaching step. Testing with excess magnesium at said pulp after MMBA / DTPA pretreatment showed no effect on brightness. Without wishing to be bound by any theory, it is believed that the lack of effect on the brightness may be due to the addition of water glass during the bleaching step. In this case, water glass seems to work in the same way as magnesium in kraft pulp.

Example 6 MMBA as a Replacement Water Glass The mass used for these tests was pretreated with DTPA. Samples were bleached with peroxide (40 kg / t pulp) and alkali was optimized. Water for comparative bleaching (40 kg / t pulp) was used. In the tests, the water glass was gradually replaced by the MMBA in the manner shown in Figure 7. The results show that the water glass produces the highest brightness. The large amount of MMBA has apparently over-stabilized the peroxide and has therefore resulted in a lower brightness of v 30. It also appears that peroxide residues are very high in the case of these samples.

I An additional test was performed using MMBA as a replacement for water glass, and this time the amounts added were 2 to 35 6 kg / t pulp. Previous tests have shown that a longer 111965 22 bleaching time ... lightness when using the MMBA in the bleaching step. Therefore, in the case of MMBA containing samples, the bleaching time was set to 4 h. In the case of a control sample containing water glass, the bleaching time was 2 h ta-5 according to the usual procedure. Figure 8 shows that adding 4 kg MMBA / t pulp achieves the same brightness as 45 kg water glass / t pulp. Tests were also performed on the pulp pre-treated with DTPA and using DTPA as a replacement for water glass. The results show that DTPA does not produce higher brightness than MMBA or water glass.

Example 7

Another chelating agent, DMAMDPA, was also tested as a complexing agent in the pretreatment step (Q step) and as a water glass substitute in the bleaching step (P step). Tests were performed with 6 kg DMAMDPA / t pulp.

Ά. Complexation step (Q step)

After pretreatment, the pulp was dewatered and washed with deionized water, and then a fresh dewatering was performed before determining the metal content of the pulp.

The manganese and magnesium contents of the pulp after the Q step are shown in Figures 9 and 10. The optimum pH at low manganese content is about 8. It appears that DMAMDPA is less sensitive to alkali changes than 25 MMBA.

B. Bleaching Phase (P Phase). Q-pulp with manganese content; was the smallest, bleached in the P stage, following the customary procedure (Eka standard); i.e., 30 to 40 kg peroxide / t pulp and 40 kg water glass and alkali were optimized. Figures 11 and 12 show the results for brightness *; and residual peroxide. As it turns out, the reference substance

I »I

• ', 1 (2 kg DTPA / t pulp) results in slightly higher brightness than DMAMDPA.

111965 23

Example 8 DMAMDPA as a replacement for water glass A pulp treated with DTPA (2 kg / t pulp) or DMAMDPA (6 kg / t pulp) was used in the Q step.

40 kg peroxide / t pulp was used and alkali was optimized. Figures 13 and 14 show results in terms of brightness and residual peroxide. It appears that treatment with successive treatments of 2 kg DTPA / t pulp (Q phase) and 6 kg DMAMDPA / t pulp yields the best result with respect to luminance. The brightness is 0.2 units better than with DTPA and water glass.

Example 9

Bleaching with Peroxide and MMBA

The bleaching tests used mixed office waste from a Scandinavian factory. Two tests were performed with peroxide, one without MMBA and one with MMBA. Both assays were optimized for alkali; refer to Figures 15 and 16. The optimum alkali content was nearly the same in both tests, but with the addition of MMBA 20 the brightness increased by about 2% (ISO). Refer to Figure 17. As MMBA was added, the amount of residual peroxide increased. MMBA appears to stabilize peroxide, leading to more selective bleaching and less peroxide degradation. 1 »> ·

Claims (8)

111965 A process for bleaching pulp, comprising bleaching the pulp using hydrogen peroxide as the primary bleaching agent, characterized in that said bleaching step is carried out in the presence of an effective amount of at least one biodegradable 1-aminoalkane-1,1-diphosphonate chelating agent of formula (I), OX OX io I'll 0. P - C - P = 0 (I) I O O N O X / R 2 R 3 wherein R 1 is hydrogen; R 2 and R 3 are hydrogen, C 1 -C 22 -alkyl groups, C 5 -C 6 -cycloalkyl groups, C 1 -C 10 -alkanol groups and carboxyalkyl groups of up to 10 carbon atoms or R 2 and R 3 together with the nitrogen atom can form piperidino, pyrrolidino or morpholino group; and X is hydrogen, alkali metal or ammonium; to promote pulp bleaching. Process according to Claim 1, characterized in that 0.01 to 2.0% by weight of said biodegradable chelating agent, based on the total weight of 1 1 • ”· 25 mass, is used. *: · 1. A process according to any one of claims 1 and 2, characterized in that 0.01 to 2.0% by weight of another additive is used, which includes citric acid, DTPA, EDTA, DTPMP and gluconates 30 and lignosulfonates having chelating activity, based on the total weight of the pulp. A process according to any one of claims 1 to 3, characterized in that said bleaching step is carried out in the presence of at least one of 0.1 to 3.0% by weight of at least one silicate and at most 1 1 1 I (> 111965) 0.2% by weight of magnesium sulphate, calculated on the total weight of the pulp. Process according to any one of claims 1 to 4, characterized in that said bleaching step is carried out at a temperature in the range of 40 to 95 ° C and in a pH range of 9 to 12 and lasts for 10 to 120 minutes and the amount of hydrogen peroxide used 0% by weight based on the total weight of the pulp. Process according to any one of claims 1 to 5, characterized in that said chelating agent is 4-morpholinylmethylene-1,1-diphosphonic acid. A chelating agent of formula (I), 0X R10X 15 I 1 'I o = p - c - p = o (I) I I 0X N 0X / R 2 r 3 wherein R 1 is hydrogen; R 2 and R 3 are hydrogen, C 1 -C 22 -alkyl groups, C 5 -C 6 -cycloalkyl groups, C 1 -C 10 -alkanol groups and carboxyalkyl groups of up to 10 carbon atoms or R 2 and R 3 may be taken together with the nitrogen atom to form piperidino -, pyrrolidino or morpholino groups -; and X is hydrogen, alkali metal or ammonium; use of water; ·. to promote bleaching of the pulp with nitric oxide, to purify the pulp or to pretreat the pulp with hydrogen peroxide before bleaching the pulp. ;;; The use according to claim 7, wherein the * 1 · '· * 30 chelating agent is 4-morpholinylmethylene-1,1-diphosphonic acid and the pulp is a mechanical pulp. 1 * »111965